Fluid dynamic lift generating or control force generating structures

ABSTRACT

In a fluid dynamic structure having an outer wall or skin defining a fluid dynamic profile part of the outer wall is flexible and has movable support apparatus and power apparatus are provided for effecting movement of the support apparatus and the flexible part whereby the fluid dynamic profile of the structure is changed. The invention is applicable to the leading edge of an aircraft wing and also to auxiliary control surfaces such as flaps and ailerons.

United States Patent [191 Pierce Feb. 13, 1973 [541 FLUID DYNAMIC LIFTGENERATING 1,880,019 9 1932 Harper ..244 44 OR CONTROL FORCE GENERATING2,010,549 8/1935 ..244/44 STRUCTURES 2,022,806 12/1935 ..244/442,223,335 11/1940 Stewart ..244/44 Inventor: a d P Aldershot, 2,523,4279/1950 Hampshire ..244/44 Hampshire, England [73] Assignee: Minister ofTechnology in Her Primary Examiner-Milton Buchler Britannic wmjestyvsvGovernment of Assistant Examiner-Stephen G. Kunln the United Kingdom ofGreat Britain Attorney-Cameron, Kerkam, Sutton, Stowell & and NorthernIreland, London, En- Stowe gland [57] ABSTRACT [22] Filed: June 1, 1970In a fluid dynamic structure having an outer wall or [21] Appl' 42082skin defining a fluid dynamic profile part of the outer wall is flexibleand has movable support apparatus and [52] us. Cl ..244/123, 244/44 p wr pp r us r provi for ff cting movement [51] Int. Cl ..B64c 3/48 of thesupport apparatus and the flexible part whereby [58] Field of Search.....244/1 23, 44 the fluid dynamic profile of the structure is changed.[56] keerences Cited The invention IS applicable to the leading edge ofan aircraft wing and also to auxiliary control surfaces UNITED STATESPATENTS such as p and ailerons v 3,179,357 4/1965 Lyon ..244/44 9Claims, 5 Drawing Figures mum-mums 3,716,209

FIG. 2.

FLUID DYNAMIC LIFT GENERATING OR CONTROL FORCE GENERATING STRUCTURES Thepresent invention relates to fluid dynamic lift generating or controlforce generating structures.

In one important aspect the invention concerns aircraft wings but isequally applicable to other lift or control force generating aircraftstructures such as a tailplane, rudder, flap, aileron or-elevator.

The main wing structure of an aircraft is designed to have efficientaerodynamic characteristics, i.e. it is shaped to provide the requiredlift with the least possible drag. The aerodynamic shape of the wing isnecessarily a comprise in that the most efficient profile for high speedflight, say typical aircraft cruising speed, differs from that which isrequired to provide the desired lift and drag characteristics at lowspeeds such as at take off and landing.

With a view to overcoming this difficulty aircraft wings are providedwith various movable auxiliary control surface structures such astrailing edge and/or leading edge flaps. These flaps are normally heldin a retracted position at cruising flight speed but at landing or takeof? speeds are extended to change the overall profile of thewing/control surface structure combina tion thereby altering the airflowover it and generating additional lift.

Also, other conventional auxiliary control surface structures such asailerons, elevators and rudder are provided which are movable togenerate, aerodynamically, control forces to enable an aircraft to bemaneuvered about roll, pitch and yaw axes.

The provision of such auxiliary control surface structures and thenecessary power means for moving them entails additional weight andcomplication and therefore affects the overall economic efficiency of anaircraft.

For aircraft capable of flight at high speedwhen local air flowvelocities are supersonic and shock waves may normally be present, whichmay involve a loss of lift and a high drag, it would be desirable if theonset of such shock waves could be delayed and/or their strengthreduced.

The present invention has for an object to provide an improved fluiddynamic lift generating or control force generating structure.

In a fluid dynamic lift generating or control force generating structurehaving an outer wall or skin defining a fluid dynamic profile and arigid internal structure, according to the present invention, part ofthe outer wall or skin is flexible and has movable support means andthere is provided power means for applying a control force to effectboth movement of said support means and flexure of said flexible partand thereby to change the fluid dynamic profile of the structure.

In the case of an aircraft wing the supportmeans and power means maytogether comprise an extensible power actuator, such as an hydraulicjack, pivotally secured at itsone end to the rigid internal wingstructure and at its other end pivotally to theflexible part of theouter wallor skin. By changing the length of the extensible member itsother end is moved to cause flexure of the flexible part and thus toeffect profile change.

The support means may also comprise at least one frame or arm memberpivotally secured at its one end to the flexible part ata movableconnecting point and at its other end pivotally to a fixed or movableconnecting point.

Thus, in a simple case the leading edge section of a wing is formed offlexible and resilient sheet material capable of supporting theaerodynamic forces involved. A swinging arm is pivotally secured at itsone end to a rigid part of the internal wing structures, such as themain spar, and is pivotally supported at its other end at the innersurface of the flexible leading edge section. Power means such as anhydraulic jack secured to the internal wing structure apply a controlforce either internally to the flexible section or to the swinging armand as a result said other end of the arm moves in an are about its oneend and the aerodynamic profile of the leading edge is changed.

In practice, the use of a single support means such as a swinging armmay lead to design difficulties and limitations and in some cases maynot permit the desired full range of profile changes to be achieved.

To overcome such limitations two or more swinging arms may be providedeach pivotally secured at its inner end to the fixed internal wingstructure and at its outer end to the inner surface of the flexibleleading edge section. A frame member supports the flexible sectioninternally at its front region and is pivotally mounted on the fixedinternal wing structure. The rearmost regions of the flexible leadingedge section are supported to slide, preferably externally, with respectto the surface of the remaining fixed section of the wing. Power meanssuch as an hydraulic jack are operative between the fixed internal wingstructure and the frame member to cause the latter to move about itspivot point. As a result the aerodynamic profile of the flexible leadingedge section is changed in accordance with the resulting arcuatemovement of the outer ends of the swinging arms about their inner ends.The swinging arms provide support to the flexible leading edge sectionin addition to defining its profile.

In an alternative arrangement the inner ends of the arms are pivotallysupported on a movable member, such as a rack, which is movable by powermeans with respect to the fixed internal wing structure to change thedisposition of the arms and hence change the profile of the leading edgesection.

A combination of movement of a frame member secured to the flexiblesection and movement of the inner ends of the arms may also be used toeffect profile changes.

In come cases the arms may comprise spring members such as leaf springsin which case the manner of their attachment at their inner and/or outerends need not be pivotal.

The invention is also applicable to the trailing edge of a wing or toother aircraft lift or control force generating structures such as thetailplane, rudder, ailerons, elevators or flaps.

In a further aspect the invention comprises means whereby theaerodynamic profile of an aircraft control surface structure may bechanged as disclosed above and having provision for creating a slot forairflow between the opposed surfaces, say the lower and the uppersurfaces, of a liftor control surface structure.

Thus, an aircraft lift or control force generating structure as definedabove according to this invention may itself be provided with a leadingedge portion which is movable in both senses between a retractedposition in which it fits snugly against said structure and formstherewith a continuous aerodynamic surface and an extended position inwhich a slot is formed between it and said structure.

Various embodiments of the invention as applied to the leading edge ofan aircraft main wing will now be described by way of example withreference to FIGS. 1 to of the accompanying diagrammatic drawings,wherein:

FIG. 1 is a side elevation of the leading edge portion of an aircraftmain wing embodying one form of the present invention;

FIG. 2 is a side elevation of a second embodiment of the invention;

FIG. 3 is a side elevation view similar to that of FIGS. 1 and 2 ofathird embodiment of the invention;

FIG. 4 is a side elevation of still another construction embodying theinvention for use where operating conditions are more severe, and/ormore extensive profile variations are desirable, than in the case of thearrangements illustrated in FIGS. 1, 2 and 3; and

FIG. 5 is a side elevation of a modificaiton of the structureillustrated in FIG. 4.

Referring first to FIG. 1, part of an aircraft main wing 11 has a mainspar l2 and a leading edge portion 13 secured to the main wing at A, A.The leading edge portion 13 is formed of flexible sheet material and hassufficient inherent stiffness to support the aerodynamic forces involvedbut is also supported by a set of power jacks, one of which is shown at14. The jacks 14 are each connected to a power supply 15 and have pistonarms 16. The piston arms 16 are each pivotally secured at 17 to theinner surface of the flexible portion 13 at brackets 18 and the jacks 14are pivotally secured at 19 at their inner ends to a forward structuralextension 20 from the main spar 12. The leading edge portion 13 definesthe aerodynamic profile of the leading edge of the wing.

In operation the jacks 14 are operated to extend or retract the pistonarms 16 the adjustment being made in accordance with airspeed. Thus forhigh speed flight conditions the piston arms 16 are extended so that thepivot points 17 are at 17'. The flexible leading edge portion 13 nowtakes up a profile as indicated by the dotted lines 13. At low speedconditions for landing or take off the piston arms 16 are retracted sothat the pivot points 17 are at 17". The flexible leading edge portion13 now takes up a profile as indicated by the chain dotted lines 13. Itwill be noted that the change in profile of the leading edge portion 13is achieved wholly by flexing of the portion 13.

At FIG. 2 the general arrangement is similar to that of FIG. 1. Part ofan aircraft main wing 21 has a main spar 22 and a leading edge portion23 the latter comprising flexible sheet material having sufficientinherent stiffness to support the aerodynamic forces involved. Aswinging frame member 24 is secured at its outer end to the flexibleleading edge portion 23 at 25 and is pivotally supported at 26 to aforward extension 27 from the main spar 22. The frame 24 has a crank arm28 which is pivotally connected at 29 to the piston arm 30 of apowerjack 31. The jack 31 is pivotally mounted at 32 on the main spar 22and has a connection 33 to a power source.

With this arrangement extension or retraction of the piston arm causesthe frame 24 to swing up and down, respectively, with consequent changein the profile of the leading edge portion 23. The profile change isaccommodated by flexing of the portion 23 between the frame member 24and the upper and lower surface of the main wing respectively.

Referring now to FIG. 3 in which the general arrangement is similar tothat of FIGS. 1 and 2, a flexible leading edge portion 34 is secured tothe main wing 35 at B, Band is supported at pivot points 36 by a pair ofswinging links 37 which latter are pivotally supported at 38 at theirinner ends to a piston arm 39 extending from a power jack 40. The jack40 is rigidly secured to a fixed frame 41 extending forwards from a mainspar 42 and has a connection 43 to a power source.

The piston arm 39 is shown in a retracted position (full lines) and anextended position (dotted lines) and in these positions the links 37take up corresponding positions as shown. As a result the profile of theleading edge portion 34 will be as shown in full lines with the pistonarm 39 retracted and as shown in dotted lines with the piston arm 39extended.

Whilst the examples described above with reference to FIGS. 1, 2 and 3may provide sufficient profile variation for simple cases, in othercases where operating conditions are more severe and/or more extensiveprofile variations are desirable an alternative form of constructionwill be required.

Such construction is shown at FIG. 4 and as shown therein an aircraftmain wing 44 has a main spar 45 and a flexible leading edge portion 46.A frame 47 extending forwards from the main spar provides pivotalsupport at 48 for a swinging frame 49 which supports the flexibleportion 46 at its foremost region. The frame 47 also provides pivotalsupport at 50 50 for the inner ends of a set of swinging support arms 5151. Each arm 51 is pivotally supported at 52 at its outer end tobrackets 53 secured to the flexible portion 46. The swinging frame 49has a crank arm 54 pivotally secured at 55 to the piston arm 56 of apower jack 57. The jack 57 is pivotally mounted at 58 to the frame 47and has a connection 59 to a power source. The flexible portion 46 hasbrackets 60 60 holding retaining pins or rollers 61 61 which latterengage flanged member 62 62 secured to the upper and lower surfaceregions of the main wing 44. By this arrangement the rearmost regions ofthe flexible portion 46 can slide with respect to the main wing but isretained in close contact with it. The location of the fixed pivotpoints 50 50 and hence the length of the respective arms 51 isdetermined by the profile changes which are required. Thus in this casefor aerodynamic considerations, the profile of the flexible leading edgeportion 46 is required to be varied from an upper condition D through anintermediate condition E to a lower condition F. The determination ofthe position of the fixed pivot point for the lower forward arm 51 isshown by way of example where its outer pivot 52 is shown at 52D, 52Band 52F, respectively. The point where the two bisectors of 52D 52E and52E 52F meet is the position for the fixed pivot 50 for this particulararm 51. The position of the respective fixed pivots for the other arms51 is determined in a like manner.

In operation the jack 57 is operative tohold the swinging frame 49 incondition D at cruise conditions. For lower flight speeds the jack isoperative to move the swinging frame 49 through condition E until atlanding or take off speed it is in condition F. It will be seen that asthe swinging frame 49 moves the arms 51 will swing about their fixedpivots 50 and the position of their outer ends will determine theprofile of the flexible leading edge portion 46 which they support. Atthe same time the rearmost regions of the flexible portion 46 will slidewith respect to the main wing.

With this arrangement the degree of profile variation of the leadingedge which is possible enables the aerodynamic efficiency of the mainwing leading edge portion combination over an aircrafts speed range tobe higher than in the case of a fixed profile arrangement.

Referring now to FIG. 5, this arrangement is basically similar to thatdescribed above with reference to FIG. 4 with the exception that theswinging arms 71 and the swinging frame 72 are pivotally supported at 7373 and 74, respectively on a carrier 75 which is movable with respect tothe main spar 76. The carrier is supported by the piston rod 77 of acontrol jack 78 pivotally supported on the main spar 76 and 79. Thecarrier 75 has trunnions 80 which engage guide slots as at 81 in sideplates (not shown) carried by the main spar 76. The carrier 75 alsosupports a secondary control jack 82 having a piston arm 83 pivotallysecured at 84 to a crank 85 extending from the swinging frame 72.

In operation actuation of the control jack 78 causes motion of thecarrier 75, the trunnions 80 running along the guide tracks 81.Extension or retraction of the whole leading edge section within thelimits of the guide tracks 81 is thus possible. Also, actuation of thesecondary control jack 82 causes angular movement of the swinging frame72 about the pivot point 74 and corresponding swinging motion of thearms 71 whereby the profile of the leading edge can be changed to takeup positions as shown in chain dotted lines. The jacks 78 and 82 may beoperated simultaneously.

Whilst the invention has been described above by way of example asapplied to the leading edge region of an aircraft main wing it isequally applicable to the trailing edge region or to other aerodynamiccontrol force generating structures such as a tailplane, rudder, flap,aileron or elevator.

Also, recent advances in aerodynamic fluid flow theory have enabledaerofoils to be designed which for a limited region of an aircraftsdesign speed range provide the required lift and low dragcharacteristics. The aerofoil shape chosen is therefore that which willgive required lift and low drag at the speed range in which the aircraftoperates most frequently i.e. at or near the cruising speed.- This meansthat at other aircraft speeds and particularly at landing and take offspeeds the desired high lift may not be possible with this shape ofaerofoil and the design is compromised. By the provision of meansaccording to the invention whereby the profile of an aerofoil may bechanged the overall aerodynamic efficiency of an aerofoil structure canbe improved as by these profile changes the shape of the aerofoil can bemade to be more nearly an ideal shape at different airspeeds. Suchprofile changes are not limited only to the leading or trailing edgeregions but can be applied at other regions of an aerofoil surface tochange its local profile.

In an alternative arrangement (not illustrated) the rear part of theflexible portion, instead of sliding over the main wingportion as inFIGS. 4 and 5, may be supported on a swinging frame to move arcuatefashion within the main wing portion.

Design calculations show that the application of the invention to theleading edge of an aircraft wing need not entail any weight penalty.

It is to be noted that to allow for wing flexure the various pivotalconnections may comprise universal joints.

The invention has a particular advantage in the case of aircraft havingvariable sweep wings wherein aerodynamic inefficiencies normallyattendent upon change of wing sweep may to some extent be reduced bychanges of wing profile by means of the invention.

The invention is also applicable to hydrodynamic control forcegenerating structures.

1 claim:

1. A fluid dynamic structure comprising a primary outer wall definingpart of a fluid dynamic profile,

a rigid internal first structure supporting said primary outer wall,

a control surface structure having a secondary outer wall which isflexible in at least one region thereof, an internal secondary structuresupporting said secondary outer wall, connecting means movablyconnecting said secondary structure to said rigid internal firststructure, and

power means operably connected between said rigid internal firststructure and said secondary structure operative to apply a controlforce to effect flexure of said at least one flexible region of saidcontrol surface secondary outer wall, said secondary structurecomprising a plurality of swinging arms connected at their one ends bysaid connecting means to said rigid internal first structure and attheir other ends to said secondary outer wall, at least some of theconnections between said swinging arms and said secondary outer wallbeing pivotal.

2. A fluid dynamic structure as claimed in claim 1 wherein saidsecondary structure and said power means together comprise an extensiblepower actuator which has pivot connections pivotally securing saidactuator at its one end to the rigid internal first structure and at itsother end to the flexible part of said secondary outer wall.

3. A fluid dynamic structure as claimed in claim 1 wherein at least oneregion of said control surface secondary outer wall is in slidingrelationship with part of the primary outer wall.

4. A structure as claimed in claim 3 wherein said connecting means alsocomprises a carrier member movably mounted on said rigid internal firststructure and to which said internal secondary structure is pivotallyattached, and said power means comprises first power means operablyconnected between said secondary structure and said carrier member andsecondary power means operably connected between said carrier member andsaid rigid internal first structure.

5. A fluid dynamic structure as claimed in claim 1 wherein the powermeans comprises an hydraulic jack.

LII

power means is operably connected between said rigid internal firststructure and said primary swinging arm.

8. A structure as claimed in claim 6 wherein said primary swinging armis attached at its one end to an extremity of maximum curvature of saidcontrol surface secondary outer wall.

9. A fluid dynamic structure as claimed in claim 1 wherein said controlsurface structure is a leading edge flap.

1. A fluid dynamic structure comprising a primary outer wall definingpart of a fluid dynamic profile, a rigid internal first structuresupporting said primary outer wall, a control surface structure having asecondary outer wall which is flexible in at least one region thereof,an internal secondary structure supporting said secondary outer wall,connecting means movably connecting said secondary structure to saidrigid internal first structure, and power means operably connectedbetween said rigid internal first structure and said secondary structureoperative to apply a control force to effect flexure of said at leastone flexible region of said control surface secondary outer wall, saidsecondary structure comprising a plurality of swinging arms connected attheir one ends by said connecting means to said rigid internal firststructure and at their other ends to said secondary outer wall, at leastsome of the connections between said swinging arms and said secondaryouter wall being pivotal.
 1. A fluid dynamic structure comprising aprimary outer wall defining part of a fluid dynamic profile, a rigidinternal first structure supporting said primary outer wall, a controlsurface structure having a secondary outer wall which is flexible in atleast one region thereof, an internal secondary structure supportingsaid secondary outer wall, connecting means movably connecting saidsecondary structure to said rigid internal first structure, and powermeans operably connected between said rigid internal first structure andsaid secondary structure operative to apply a control force to effectflexure of said at least one flexible region of said control surfacesecondary outer wall, said secondary structure comprising a plurality ofswinging arms connected at their one ends by said connecting means tosaid rigid internal first structure and at their other ends to saidsecondary outer wall, at least some of the connections between saidswinging arms and said secondary outer wall being pivotal.
 2. A fluiddynamic structure as claimed in claim 1 wherein said secondary struCtureand said power means together comprise an extensible power actuatorwhich has pivot connections pivotally securing said actuator at its oneend to the rigid internal first structure and at its other end to theflexible part of said secondary outer wall.
 3. A fluid dynamic structureas claimed in claim 1 wherein at least one region of said controlsurface secondary outer wall is in sliding relationship with part of theprimary outer wall.
 4. A structure as claimed in claim 3 wherein saidconnecting means also comprises a carrier member movably mounted on saidrigid internal first structure and to which said internal secondarystructure is pivotally attached, and said power means comprises firstpower means operably connected between said secondary structure and saidcarrier member and secondary power means operably connected between saidcarrier member and said rigid internal first structure.
 5. A fluiddynamic structure as claimed in claim 1 wherein the power meanscomprises an hydraulic jack.
 6. A structure as claimed in claim 1wherein said internal secondary structure comprises a primary swingingarm supporting a non-flexible region of said control surface secondaryouter wall, and a plurality of secondary swinging arms pivotallyconnected at their one ends by said connecting means to said rigidinternal first structure and at their other ends to said at least oneflexible region of said control surface secondary outer wall.
 7. Astructure as claimed in claim 6 wherein said power means is operablyconnected between said rigid internal first structure and said primaryswinging arm.
 8. A structure as claimed in claim 6 wherein said primaryswinging arm is attached at its one end to an extremity of maximumcurvature of said control surface secondary outer wall.